The vent from the water closet should be 2 in. in size, but never of smaller size.

The vent pipe is usually connected to the lead bend, but should never be connected to the crockery itself, as such a connection must necessarily be rigid, and the settling of floors, slight movement of the fixture, etc., will result in breaking off the vent horn.

When connected to the lead bend the vent should always be taken from the top of the horizontal part of the bend - never from the vertical part, as when so constructed it is much more liable to stoppage.

Fig. A shows an excellent method of venting from the vent hub of a vented T-Y, a common stock fitting, the vent pipe being of cast or wrought iron.

Fig. B shows the use of special waste and vent fittings, of which numerous styles are now on the market.

This waste fitting is so arranged that the branch to the fixture enters the side of the main body of the fitting, thus allowing the fixture to set closer to the wall than is possible with the waste fitting of Fig. A. Work such as shown in these two illustrations is growing in favor, and serves to show the decadence of lead work and the increase in the use of cast and wrought iron in plumbing construction.

Venting being employed chiefly to prevent the siphonage of fixture traps, it is unnecessary to vent a water closet which is located close to its stack and in a position secure from siphonic influences. A water closet set close to the stack, on the top floor, and without other fixtures on that floor wasting into the same stack, is an example of this. A water closet located at a considerable distance from its stack, however, should always be vented, for through the long horizontal connection the waste would necessarily move slowly, particularly if the pipe were nearly level, and an obstruction, such as might be caused by paper, etc., might result in setting the water back sufficiently to fill the pipe, and this body of water in flowing out might create sufficient suction to partially or entirely destroy the seal of the water-closet trap.

In the case of fixtures located on floors above the water closet the influence of siphonic conditions may also be felt, for as waste from these fixtures descends in large volume past the entrance of the lead bend, the air becomes somewhat exhausted, and is not renewed quickly enough to prevent a part of the trap seal being siphoned or sucked out.

This loss may amount to but a few drops, but when continued indefinitely may result in the complete loss of seal, aided, as it often is, by additional loss due to evaporation in the case of fixtures seldom used.

As far as the siphonage of the water-closet trap is concerned, this danger is less to be feared than in connection with smaller traps, for the reason that to produce siphonage of a column of water 4 inches in diameter requires much stronger influences than to produce the same result on smaller traps.

Nevertheless, the water-closet trap is probably much more subject to siphonage than it is generally supposed to be, and if strict ordinances regarding its protection were not established and enforced, the trouble arising from this cause would be much more extensive than it now is.

There is probably no part of the plumbing system which occasions so much trouble as the ball cock which supplies the water-closet flush tank with water.

Two styles of ball cock are in use, the bottom supply and the top supply.

Bottom supply makes neater looking work, but in other respects the advantage seems to be with the top supply.

In the bottom supply the ball cock is located at the bottom of the tank, while in the top supply it is at the top, and therefore much more accessible in the event of repairs. This is especially true of tanks located close to ceilings.

Under these conditions, if provided with a bottom supply, the tank must be taken down to repair the ball cock, while in the case of top supply it can usually be repaired without such inconvenience. Ball cocks may be further divided into two classes, direct and indirect pressure. The indirect pressure ball cock, which is commonly used and least expensive, is generally provided with a 5 or 6 inch copper ball, which closes the valve by its buoyancy. The direct pressure ball cock works on another principle than the indirect, the water being conducted to the rear of the plunger, thereby adding the force of the water pressure to the buoyancy of the float in closing the valve. In the direct pressure ball cock, a heavy ball or float must be used, as a considerable weight is necessary to enable the ball cock to open against pressure. The light copper ball used on the indirect pressure ball cock would be inadequate to perform this duty.

Glass floats are now much in favor in connection with ball cocks, as they provide sufficient weight and are more durable than the copper floats which are now largely used.

As a result of keen competition, copper floats are now largely made of sheet copper that is so thin that it can withstand almost no rough usage.

Some of the necessary requirements in a ball cock is that it shall be as nearly noiseless as possible, quick closing, easy to repair, of simple construction, and made of a high grade of metal free from impurities, so that the water may not act chemically upon the valve seat and destroy it.